In automotive vehicles, it is common to have a climate control system located within an instrument panel which provides heated or cooled air to occupants through dash panel defrost air outlets, instrument panel venting air outlets and floor directed air outlets. These traditional climate control systems often include a heater core that performs heat exchange between the engine coolant, which is heated by the engine, and the cool air in the cabin/outside environment in order to provide warm air to the passenger compartment. Some vehicles include an air conditioning system that incorporates an evaporator for absorbing heat from the air in the vehicle. The heater core and evaporator are typically provided in an HVAC module case located in the passenger compartment of the vehicle.
In some vehicles, the climate control system is adapted to control three zones of the cabin space. Generally, the three zones include the front driver's side, the front passenger's side and the rear occupant zone. The HVAC case typically includes ducting to accommodate air distribution to these appropriate zones as desired. Air mix doors may be provided for modifying the temperature of air passed through the ducting to the occupants of the vehicle. In one example, a front air mix door (or doors) is provided for modifying the temperature of air passed into the front cabin and a rear air mix door (or doors) is provided for modifying the temperature of air passed into the rear cabin. Typically, a pair of servo motors are provided for independently controlling the respective front and rear air mix doors. In some applications however, multiple servo motors may be cost prohibitive.